Vietnam's President Truong Tan Sang makes rare White House visit (VIDEO)

Vietnam's President Truong Tan Sang met with United States President Barack Obama at the White House in Washington, DC, on Thursday.

It's the first time Sang has visited Washington and only the second time a Vietnamese president has visited the Oval Office since the US and Vietnam normalized relations in 1995.

The talks focused on trade, with the two leaders reaffirming their commitment to finishing a comprehensive Trans-Pacific Partnership free trade agreement as soon as possible this year.

Vietnam's largest trading partner is China, but with recent spats between the two countries over territory in the South China Sea, Vietnam is keen to broaden trade ties elsewhere, the Wall Street Journal noted.

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"Five years after entering the World Trade Organization and experiencing recent global financial crisis, Vietnamese leaders have realized that they should learn more from the US to be able to overcome economic challenges as the country wants to head to the market economy," economist Vuong Hoang from DHVP Research & Consultancy told the WSJ.

But Obama said at a press conference that he also raised the issue of Vietnam's crackdown on free speech.

"The United States continues to believe that all of us have to respect issues like freedom of expression, freedom of religion, freedom of assembly," Obama said. "We had a very candid conversation about both the progress that Vietnam is making and the challenges that remain."

Before meeting with Obama, Sang said his government has been making "sustained efforts to promote human rights."

On Wednesday, Sang attended a lunch hosted by US Secretary of State John Kerry at the State Department.

"Forty-five years ago, hundreds of thousands of Americans were fighting in the fields and rivers of Vietnam," Kerry, a veteran of the Vietnam War, remarked at the lunch. "Today, hundreds of thousands of us are visiting its market places and its historic sites. So we have come a long way."